Asda and Molson Coors have joined with Leaf to develop water management guidance for farmers and suppliers, in the face of increasingly unpredictable weather. Photograph: Bailey-Cooper Photography 3 / Al/Alamy

Farmers, it's said, always want "weather by the field". Certain crops require more rain, others less. Some thrive in shady conditions, others need sun all day long. Today, farmers are less exacting: they'd be happy with some simple predictability.

Future proofing farming

Farmers need to face up to the reality of "increasingly unpredictable weather," says Caroline Drummond, chief executive of sustainable farming group Leaf. To help them on their way, Leaf has launched a six-step guide on sustainable water management. The steps cover ways to save water, protect water sources, manage the soil, install effective drainage and monitor water consumption.

"Farmers tell us that they can cope with one bad year of drought or heavy rains, but the impact of two bad years makes it much harder to ensure their business remains resilient," Drummond explains.

The idea of weather-resilient agriculture chimes with supermarket Asda, which worked with Leaf to develop the advisory guide. "We see this as part of future proofing the industry and building capacity so that farmers are equipped to implement necessary changes," says Chris Brown, head of ethical and sustainable sourcing at the British supermarket.

For a retailer like Asda, which sources stock from thousands of farms across the UK, it doesn't take long before water problems in the countryside morph into problems in its stores. It's all connected, Brown explains. Excessive rains mean a bad cereal crop, which means more expensive animal feed, which means higher food prices at the till.

The initiative's other corporate backer is brewer Molson Coors. The company purchases around 30,000 tonnes of barley from UK farmers every year. Security of supply is therefore a driving factor as well. But so too is water quality. As Debbie Read, Molson Coors' corporate responsibility manager, puts it: "Without great quality water, you can't make great quality beer."

No-nonsense advice

Will the initiative deliver? If it comes down to the advice itself, there's no reason it shouldn't. The measures are all "easy to understand without being patronising," insists Sarah Mukherjee, director of environment at Water UK. Furthermore, they're clearly "written by people who knew what they were talking about." So, for example, farmers should clear drainage ditches, fence livestock away from water courses and clear up fertiliser spillages. Rocket science, it isn't.

A video shows how Overbury Farms, a Leaf demonstration farm in Gloucestershire, is using responsible water management techniques.

To Matthew Naylor, whose Lincolnshire farm sits on silt soil with little access to non-salty water, the measures make perfect sense. To date, he's installed rain-harvesting equipment on his packing and cold stores, as well as investing in a water-efficient trickle irrigation system. He is currently looking to put in a lined 'bio-bed' to decompose pesticides in the event of spillages. He credits these steps with increasing both the yields and quality of his produce, which he sells to most of the UK's largest supermarkets.

Naylor cites other benefits too. One is what he terms "the licence to supply". Large retailers increasingly want assurances of sustainable production process, he says. Leaf operates a certification scheme designed to provide just such guarantees. Another important factor is cost saving. Water accounts for 1% of a farm's fixed costs, with more than eight in 10 (83%) of farmers using water directly from the mains, according to government figures. Naylor, who features in that number due to the salt content of his underground water supply, admits that using drinking water for irrigation is "really quite extravagant".

Whether more farmers will follow his lead is the key issue at stake. Both Molson Coors and Asda are promoting the six-steps among their supply base. Arguably, it's easier for Molson Coors, which sources from around 100 main suppliers. The brewer is planning to run regional-level workshops with all of these to discuss their experience of applying the six-step model. Asda, meanwhile, will focus initially on its dairy farmers. That makes sense. Drinking water for livestock accounts for around two-fifths (41%) of all water use in the UK agriculture sector.

Policy pressure

If the economic logic for responsible water management doesn't persuade farmers, then regulatory pressure just might. Leaf's Drummond accepts that at present the UK has no "integrated, risk-based policy" for either drought or flooding. At present, the only obligation on farmers is to use public water legally. Under the common agricultural policy, farmers need a licence to take water from UK rivers or use groundwater resources.

Where the rules get tougher is under the EU water framework directive, which covers water use in major catchments areas. "In many catchments, there is no more water available to meet everyone's needs, and measures will be taken to restore the balance," says Paul Hammett, a water specialist at the National Farmers Union. But it remains "too early to say" what these measures will be, he admits. It's one for farmers to watch, however, especially those located in regions of high water sensitivity.

Ultimately, the most compelling reason for farmers to sit up and take note is the weather itself. As Hammett concludes: "Farmers understand that they must get even better at managing with limited water supply to prepare for the next drought – because there will be a next time."